1. Technical Field
The subject matter described here generally relates to wind turbines, and, more particularly, to stackable nacelles for wind turbines.
2. Related Art
A wind turbine is a machine for converting the kinetic energy in wind into mechanical energy. If that mechanical energy is used directly by machinery, such as to pump water or to grind wheat, then the wind turbine may be referred to as a windmill. Similarly, if the mechanical energy is further transformed into electrical energy, then the turbine may be referred to as a wind generator or wind power plant.
Wind turbines use one or more airfoils in the form of a “blade” to generate lift and capture momentum from moving air that is them imparted to a rotor. Each blade is typically secured at its “root” end, and then “spans” radially “outboard” to a free, “tip” end. The front, or “leading edge,” of the blade connects the forward-most points of the blade that first contact the air. The rear, or “trailing edge,” of the blade is where airflow that has been separated by the leading edge rejoins after passing over the suction and pressure surfaces of the blade. A “chord line” connects the leading and trailing edges of the blade in the direction of the typical airflow across the blade. The length of the chord line is simply the “chord.”
Wind turbines are typically categorized according to the vertical or horizontal axis about which the blades rotate. One so-called horizontal-axis wind generator is schematically illustrated in FIG. 1 and available from GE Energy of Atlanta. Ga. USA. This particular configuration for a wind turbine 2 includes a tower 4 supporting a drive train 6 with a rotor 8 that is covered by a protective enclosure referred to as a “nacelle” 20. The blades 10 are arranged at one end of the rotor 8, outside the nacelle 20, for driving a gearbox 12 connected to an electrical generator 14 at the other end of the drive train 6 arranged inside the nacelle along with a control system 16. An anemometer 18 is also provided on the nacelle 20 for providing information to the control system 16.
Modern nacelles 20 are typically assembled at a factory and then transported individually to each wind turbine 2 installation. As discussed in WIPO International Publication No. WO2007/132408, increasingly larger wind turbines require larger and larger nacelles with resulting transport difficulties. To address this problem, modern nacelles are sometimes assembled on-site from a kit including, among other things, smaller plate-shaped elements that are assembled by means of mountings at the place of use. However, such conventional techniques still require substantial logistical and assembly resources to implement at the factory and wind turbine 2 installation.